Percutaneous Vertebral Reconstruction (PVR) Technique of Pathological Compression Fractures: An Innovative Combined Treatment of Microwave Ablation, Bilateral Expandable Titanium SpineJack Implants Followed by Vertebroplasty

(1) Background: to retrospectively evaluate safety and efficacy of combined microwave ablation (MWA) and bilateral expandable titanium SpineJack (SJ) implants followed by vertebroplasty (VP) for the treatment of painful thoracolumbar pathological vertebral compression fracture. (2) Methods: from July 2017 to October 2022, twenty-eight patients (13 women and 15 men; mean age 68 ± 11 years) with a history of primary neoplasm and thirty-six painful vertebral metastases with vertebral compression fracture underwent combined MWA and bilateral expandable titanium SpineJack implants with vertebroplasty. We analyzed safety through complications rate, and efficacy through vertebral height restoration and pain decrease, evaluated using a visual analogue scale (VAS), and Functional Mobility Scale (FMS), and local tumor control. Contrast-enhanced CT scans were performed at 1, 3, and 6 months and a contrast-enhanced spine MRI at 6 months after the procedure. (3) Results: Technical success rate was 100%. No procedure-related major complications or death occurred. Vertebral height restoration was observed in 22 levels (58%), with a mean anterior height restoration of 2.6 mm ± 0.6 and a mean middle height restoration of 4.4 mm ± 0.6 (p < 0.001). Mean VAS score of pain evaluation on the day before treatment was 6.3 ± 1.5 (range 4–9). At the 6-month evaluation, the median VAS score for pain was 0.4 ± 0.6 (range 0–2) with a mean reduction of 93.65% (6.8 ± 0.7 vs. 0.4 ± 0.6; p < 0.000) compared with baseline evaluation. Contrast-enhanced CT scans were performed at 1, 3, and 6 months and a contrast-enhanced spine MRI was performed at 6 months after the procedure, showing no local recurrence, implant displacement, or new fractures in the treated site. (4) Conclusions: combined microwave ablation and bilateral expandable titanium SpineJack implants with vertebroplasty is a safe and effective procedure for the treatment of pathological compressive vertebral fractures. The vertebral stabilization achieved early and persistent pain relief, increasing patient mobility, improving recovery of walking capacity, and providing local tumor control.


Introduction
Bone metastases are a markedly widespread and common nosological entity in the context of oncological diseases.
The treatment of vertebral metastases is very complex due to the presence of severe pain associated with instability and consequent neurological deficits that determines an increase in morbidity and mortality.
Conventional therapies, such as chemotherapy, radiotherapy, hormone therapy, bisphosphonates, and analgesics, are effective in controlling pain and instability in most cases, but due to the increased incidence of spinal metastases, non-response to conventional treatments or contraindications to them, the role of interventional radiology in this field has been increased [1,2].
CIRSE (Cardiovascular and Interventional Radiology Society of Europe) guidelines indicate that vertebral augmentation techniques (VAPs) such as vertebroplasty (VPT), kyphoplasty (KPT), and vertebral implants (VI), also combined with focal ablation modalities, can be usefully and successfully combined to prevent or stabilize pathological fractures in painful vertebrae with extensive osteolysis that do not respond to conventional therapies or in combination with them [13].
Only one study in the literature explores the possibility of using SpineJack (SJ) for the treatment of vertebral fractures secondary to metastatic tumor infiltration, showing promising results [14].
The purpose of our study is to describe an innovative percutaneous combined treatment composed of microwave ablation (MWA) with bilateral expandable titanium Spine-Jack implants followed by vertebroplasty and to evaluate its safety and efficacy for the management of refractory painful vertebral metastases, assessing pain reduction, and vertebral structural restoring.

Materials and Methods
This study was approved by the ethics committee of our institution. Informed consent was obtained from all individual participants included in the study. This is a single-center retrospective study including 28 patients (13 women and 15 men; mean age: 64 years, range 41-80 years) with a history of primary neoplasm (8 breast carcinoma, 5 non-small cell lung cancer, 2 kidney, 2 thyroid, 2 oral cavity, 2 pancreas, 2 derwent combined MWA with bilateral expandable titanium SpineJack implants followed by vertebroplasty ( Table 1).
The inclusion criteria were the presence of vertebral metastasis determining a vertebral body stress fracture detected on computed tomography (CT) or magnetic resonance imaging (MRI) scan, in patients with life expectancy greater than 2 months.
The VAS score was subsequently evaluated at 1 week and 1, 3, and 6 months follow-up. The FMS was recorded 1 month after the treatment to assess the effect of the treatment on mobility and the ability to walk. A 4-point FMS classification was used: 4, bedridden; 3, use of a wheelchair; 2, limited painful ambulation; 1, normal ambulation.
All patients performed a pre-procedural contrast-enhanced CT scan to assess the location, size, and radiological characteristics of the lesion and to define the procedural planning. The combined procedure was performed in a single vertebra in 20 patients, in 2 vertebrae in 5 patients, and in 3 vertebrae in 1 patient. In 2 patients, the procedure consisted of SJ implants and vertebroplasty without ablation because they had already been treated with MWA (Table 1). Control contrast-enhanced CT scans were acquired 3 and 6 months after the procedure according to routine oncologic follow-up.
Drug therapy (NSAIDs and opioids) was discontinued 1 week after the treatment and resumed in cases of persistence or exacerbation of painful symptoms. Antibiotic prophylaxis was administered 30 min before the start of the procedure with a single dose of 2 mg of i.v. cefazolin.
The combined treatment of MWA and expandable titanium SpineJack implants was performed under dual CT guidance and fluoroscopy guidance to allow the correct positioning of the antenna, evaluate the ablation area, obtain a correct visualization during advancement and expansion of the SJ implants, control potential posterior wall protrusion and monitor any leaks during cement injection.
After periosteum anesthesia with bupivacaine hydrochloride at 0.9% using 18 Gauge Chiba needle, two 10 Gauge beveled bone needles (Thiebaud Biomedical Devices, Margencel, France) were directly inserted into the posterior aspect of the vertebral body via a bilateral transpedicular approach.
Through this access, the microwave antennas were inserted coaxially for the ablation. Percutaneous MWA was performed using a 2.45 GHz microwave generator (AMICA-GEN, HS Hospital Service, Aprilia, Italy) which supplies energy through a 14-gauge interstitial antenna, mini choked, and water-cooled (AMICA-GEN).
If the metastasis was limited to half of the vertebral body, the lesion was ablated using a single 14-gauge antenna.
If the lesion exceeded the midline of the vertebral body, 2 MWA antennas were positioned with bi-pedicle access.
Once the ablation was finished, the microwave needles were removed and two blunt guidewires (Stryker, Rome, Italy) were inserted coaxially through the same access cannula repositioned in the posterior vertebral third, up to the anterior vertebral third.
A designed drill (Stryker) mounted on a working cannula was gently advanced coaxially into the vertebral body until the desired position of the implant, approximately up to 5 mm from the anterior wall.
After the removal of the first drill, an acrylic plug is left in place until both bone canals have been prepared for implantation. When the drill was then removed, the working cannula was left on site to allow the subsequent introduction of the implants.
After preparation of both sides, the two SpineJacks ® (Stryker Corp, Kalamazoo, MI, USA) were inserted into the vertebral body through the working cannulae and were gradually and simultaneously deployed, under fluoroscopic control, by turning the expanders" handles clockwise until height restoration and kyphosis reduction were judged satisfactory.
The implants were detached by unscrewing the quick-release pin at the tip of the handles.
Finally, poly-methyl-methacrylate (PMMA) bone cement (SpinePlex ® radiopaque bone cement; Stryker Corp, Kalamazoo, MI, USA) was slowly injected under real-time fluoroscopy through the same working cannula into the vertebral body and around the devices until the optimal filling was obtained. Following the injection of cement, the working cannulas were extracted.
An immediate post-procedural no contrast-enhanced CT scan was performed to evaluate the results and any complications ( Figure 1).
All patients were followed up for up to six months. The details of the spine jack positioning procedure are described in Figure 2. All patients were followed up for up to six months. The details of the spine jack positioning procedure are described in Figure 2.

Statistical Analysis
For the purposes of this study, continuous variables were reported as mean ± standard deviation (SD). Differences between the average VAS score at 1 week, 1, 3, and 6 months and FMS at 1 month after the procedure was evaluated by means of Student's ttest or Fisher's exact test as appropriate. A p-value less than 0.05 was taken as significant. Statistical analysis was performed using OpenStat software version 11.9.08.

Results
A total of 76 expandable titanium SpineJack implants were inserted into 38 vertebrae. The levels of the treated vertebrae can be seen in Figure 3.

Statistical Analysis
For the purposes of this study, continuous variables were reported as mean ± standard deviation (SD). Differences between the average VAS score at 1 week, 1, 3, and 6 months and FMS at 1 month after the procedure was evaluated by means of Student's t-test or Fisher's exact test as appropriate. A p-value less than 0.05 was taken as significant. Statistical analysis was performed using OpenStat software version 11.9.08.

Results
A total of 76 expandable titanium SpineJack implants were inserted into 38 vertebrae. The levels of the treated vertebrae can be seen in Figure 3. Minimal leakage of cement occurred in three procedures (8%), one anterolateral, one posterolateral and one intradiscal leakage, without clinical impact.
Two patients developed a secondary vertebral fracture in a caudal segment, respectively, 7 and 10 days after the procedure.
Both adjacent fractures were successfully treated with implantation of SpineJack implants (Patient 4 and 15 Table 1).
Vertebral height restoration was observed in 22 vertebrae (58%), with a mean anterior column height restoration of 2.6 mm ± 0.6 and a mean middle column height restoration of 4.4 mm ± 0.6 (p < 0.001) (Figure 4).  Minimal leakage of cement occurred in three procedures (8%), one anterolateral, one posterolateral and one intradiscal leakage, without clinical impact.
Two patients developed a secondary vertebral fracture in a caudal segment, respectively, 7 and 10 days after the procedure.
Both adjacent fractures were successfully treated with implantation of SpineJack implants (Patient 4 and 15 Table 1).
Vertebral height restoration was observed in 22 vertebrae (58%), with a mean anterior column height restoration of 2.6 mm ± 0.6 and a mean middle column height restoration of 4.4 mm ± 0.6 (p < 0.001) (Figure 4). Minimal leakage of cement occurred in three procedures (8%), one anterolateral, one posterolateral and one intradiscal leakage, without clinical impact.
Two patients developed a secondary vertebral fracture in a caudal segment, respectively, 7 and 10 days after the procedure.
Both adjacent fractures were successfully treated with implantation of SpineJack implants (Patient 4 and 15 Table 1).
Vertebral height restoration was observed in 22 vertebrae (58%), with a mean anterior column height restoration of 2.6 mm ± 0.6 and a mean middle column height restoration of 4.4 mm ± 0.6 (p < 0.001) (Figure 4).  All patients were discharged 24 h after the treatment in stable and uncomplicated conditions.
All patients were discharged 24 h after the treatment in stable and uncomplicated conditions.
Three of the seven patients who reported the use of a wheelchair before the procedure acquired normal ambulation 1 month after the procedure.
All seven patients who presented limited, painful ambulation before the procedure improved mobility and reported normal ambulation after the procedure. One month after treatment, the median VAS score was 0.5 ± 0.6 (range, 0-3) with a mean reduction of 92.06% (6.8 ± 0.7 vs. 0.5 ± 0.6; p < 0.000; Figure 5) compared with baseline evaluation.
Three of the seven patients who reported the use of a wheelchair before the procedure acquired normal ambulation 1 month after the procedure.
All seven patients who presented limited, painful ambulation before the procedure improved mobility and reported normal ambulation after the procedure.
Of the four bedridden patients, two reported limited painful ambulation after one month, and the other two improved mobility acquiring normal ambulation one month after the procedure. During follow-up, no infectious complications were observed.
Contrast-enhanced CT scans performed at 1, 3, and 6 months and contrast-enhanced spine MRI performed at 6 months after the procedure showed no local recurrence, implant displacement, or new fractures in the treated site ( Figure 6).
Of the four bedridden patients, two reported limited painful ambulation after one month, and the other two improved mobility acquiring normal ambulation one month after the procedure. During follow-up, no infectious complications were observed.
Contrast-enhanced CT scans performed at 1, 3, and 6 months and contrast-enhanced spine MRI performed at 6 months after the procedure showed no local recurrence, implant displacement, or new fractures in the treated site ( Figure 6).

Discussion
Bone metastases, which are frequently localized in the spine, can affect more than half of patients with a history of malignant tumors and are often the cause of pain, instability, and disability, affecting the quality of life.
Given the complexity of metastatic bone pathology and its clinical consequences, a multidisciplinary approach is required.

Discussion
Bone metastases, which are frequently localized in the spine, can affect more than half of patients with a history of malignant tumors and are often the cause of pain, instability, and disability, affecting the quality of life.
Given the complexity of metastatic bone pathology and its clinical consequences, a multidisciplinary approach is required.
The most used systemic and focal therapies for the treatment of bone metastases are chemotherapy, radiotherapy, hormone therapy, bisphosphonates, and analgesics [1].
In 2017, Tsoumakidou et al. pointed out in the CIRSE guidelines that vertebra augmentation techniques, such as vertebroplasty, kyphoplasty, and vertebral implants, are indicated in the treatment of vertebral compression fractures.
These treatments are also indicated for painful vertebrae fractures with extensive osteolysis due to malignant infiltration by multiple myeloma, lymphoma, and metastasis that do not respond to conventional therapies or in combination with them [14].
Vertebroplasty, while improving the pain associated with vertebral collapse, does not allow recovery of the vertebral body height and prevent spinal deformity, which can sometimes be associated with new vertebral fractures.
Furthermore, VPT does not allow a suitable action in the local treatment of the tumor and is associated with a moderate rate of cement leaks [15]. Balloon kyphoplasty and other vertebral implants have been developed to further improve the cement deposition and stabilization of cancer-related fractures [16,17]. SpineJack is an expandable intravertebral titanium implant that allows the restoration of vertebral height and the maintenance of a correct kyphotic angle of the spine resulting in a more balanced distribution of the craniocaudal thrust forces on the fractured vertebrae and on the whole spinal column [18]. It is widely used in the treatment of vertebral compression fractures [19][20][21][22][23][24][25].
Follow-up studies directly comparing SpineJack implant to KPT in the treatment of vertebral post-traumatic compression fractures demonstrated that the vertebral height correction obtained with SJ is associated with less spinal deformity; less cement is used than with KPT and the incidence of adjacent fractures is significantly less in SJ (3 to 5%) compared to 15-20% with KPT [26,27].
In 2022, Cornelis et al. published a single-center retrospective review study on 13 patients to evaluate the applicability of SJ, using cone-beam CT guidance, in the treatment of vertebral fractures secondary to tumor infiltration with promising results [16].
Our results are similar in terms of technical success without major complications confirming that it is a feasible and safe procedure.
Unlike that study, all our patients underwent procedures under conscious sedation and local anesthesia, with no need for general anesthesia.
We believe that the use of CT scan in combination with fluoroscopic guidance allows both a correct positioning of the MWA antennae and SJ implants without significant side effects or procedural complications.
The idea of combining ablation treatment with SJ implantation prior to vertebroplasty is based on different scientific assumptions. The 2022 CIRSE guidelines indicate that in load-bearing and long bones, ablation and consolidation can be usefully combined to effect ablation and palliation and prevent or stabilize pathological fractures, and if the goal of the treatment is curative, percutaneous osteoplasty should always be preceded by a definitive ablative treatment [13].
In 2020, guidelines in Oncology (Bone health in cancer: ESMO Clinical Practice Guidelines), the use of combined ablative percutaneous therapies and VAPs in the treatment of spine metastases were suggested to obtain pain relief and tumor burden reduction in bone.
Minimally-invasive ablation techniques and VAPs are used in combination to reduce tumor mass, create a cavity and stabilize the vertebral body [28]. Mohme et al. observed that peripheral circulating tumor cells (CTCs) are significantly increased due to vertebral cement augmentation procedures, justifying the rationale of combined ablation techniques option to reduce the increased release of CTC associated with cementoplasty [29].
A systematic review of the literature by Sagoo et al. confirmed that the use of MWA, associated with vertebroplasty to treat patients with painful vertebral metastases, is capable of achieving both effective pain relief and local disease control, as already evidenced in previous studies [30][31][32][33].
The pathological replacement of a vertebral body is associated both with the phenomena of osteolysis and the cause of pain, and often with structural subversion based on trabecular collapse and extra-vertebral extension.
The purpose of the combined treatment of ablation with SJ implant and vertebroplasty is the structural recovery of the vertebra so as to obtain both an analgesic effect and recovery of the patient's mobility.
The restoration of the vertebral body affected by pathological collapse with a minimally invasive percutaneous approach is the main innovative aspect of the technique and, although a limited sample, the procedure allows recovery of height, even of severe pathological vertebral collapse, as shown in Figure 7.
The pathological replacement of a vertebral body is associated both with the phenomena of osteolysis and the cause of pain, and often with structural subversion based on trabecular collapse and extra-vertebral extension.
The purpose of the combined treatment of ablation with SJ implant and vertebroplasty is the structural recovery of the vertebra so as to obtain both an analgesic effect and recovery of the patient's mobility.
The restoration of the vertebral body affected by pathological collapse with a minimally invasive percutaneous approach is the main innovative aspect of the technique and, although a limited sample, the procedure allows recovery of height, even of severe pathological vertebral collapse, as shown in Figure 7.  The main novelty of the method is based on the introduction of the combined ablative and VTP treatment of the intermediate step of the vertebral SJ implant in order to recover the vertebral morphology, realign the column loading curve, and to resolve the posterior compression phenomena caused by the disease's epidural extension. In our sample of treated patients, during the imaging follow-up, it was found that the recovery of the height of the anterior wall and the middle third of the vertebral body led to a realignment of the posterior wall as well. The recovery of both vertebral height and morphology results in a reduction of the extra-vertebral extension and epidural compressive phenomena [34].
The technical success is also associated with the improvement of two clinical aspects related to vertebral collapse. First, a recovery of bone height and consistency guarantee both analgesic and functional improvement, the gaining of pain control, and recovery of lost mobility.
Second a local tumor control thanks to the combined use of ablative techniques and cementoplasty. In our experience, the probability of VPT-related fracture of the treated and distant vertebrae is also reduced, and the cement distribution is improved, reducing procedural leaks.
In the small cohort examined, we obtained encouraging results in terms of the technical success, analgesic response, and recovery of the patients' mobility. Furthermore, no residue or local recurrence was identified in the treated sites during follow-up. Therefore, we believe that this innovative procedure PVR could represent a further treatment option for advanced vertebral involvement when severe bone collapse and extra-vertebral extension limit safe vertebroplasty.
This study has some limitations, such as the small sample size, single-center study, retrospective design, no control group, and short duration of follow-up.
Despite these limitations, PVR represents a promising new approach in the minimally invasive landscape of spine metastases treatment, combining pain reduction, increased spine stability, and local tumor control.

Conclusions
This preliminary result suggests that a combined treatment of microwave ablation and bilateral expandable titanium SpineJack implants followed by vertebroplasty is a safe and effective procedure for the treatment of pathological compressive vertebral fractures.
The vertebral stabilization achieved allows early and persistent pain relief, increasing patient mobility, improving recovery of walking capacity, and providing local tumor control.